INBREEDING DEPRESSION FOR YIELD AND YIELD COMPONENTS IN Fragaria ananassa Duch.

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1 Acta Sci. Pol., Hortorum Cultus 11(1) 2012, INBREEDING DEPRESSION FOR YIELD AND YIELD COMPONENTS IN Fragaria ananassa Duch. El bieta Kaczmarska University of Life Sciences in Lublin Abstract. In case of plants, inbreeding can be measured through comparison of the fitness of selfed individuals with outcrossed individuals. In this paper the effect of repeated inbreeding on fruit yield and yield component of strawberries (Fragaria ananassa Duch.) was examined. Five strawberry cultivars (from 10 initial ones) including Kent, Teresa, Senga Sengana, Chandler and the breeding clone 1387 were examined and self-pollinated in order to obtain first (S 1 ), second (S 2 ) and third (S 3 ) inbreeding generations. 5 cultivars differing in pedigree which were assumed to have the inbreeding coefficient of zero (F = 0) were compared with self-pollinated populations with expected inbreeding coefficients F = 0.5 (S 1 ), F = 0.75 (S 2 ) and F = 0.87 (S 3 ). The effects of different inbreeding levels were estimated for the following traits: number of inflorescences, number of flowers per inflorescence, fruit yield per plant, fruit number per plant, average fruit weight, weight of leaves per plant and pollen viability. Both positive and negative inbreeding s were found in many progenies in terms of the analysed characters. Weight of leaves per plant in S 1, S 2 and S 3 was affected the most (inbreeding ID = 62.5, ID = 66.2 and ID = 67.2, respectively). In the second generation (S 2 ), average fruit number per plant increased in comparison to S 0 (ID was -6.1). Inbreeding for average fruit weight per plant decreased in the successive inbreeding generations. Key words: ID, strawberry, fruit yield characters, repeated inbreeding INTRODUCTION Inbreeding appears universally to reduce fitness, but its magnitude and specific effects are highly variable because they depend on the genetic constitution of the species or populations and the fact how these genotypes interact with the environment [Alam at al. 2004]. Inbreeding (ID) and heterosis are related phenomena of fundamental importance for evolutionary biology and applied genetics. Inbreeding refers to Corresponding author Adres do korespondencji: El bieta Kaczmarska, Department of Genetics and Plant Breeding, University of Life Sciences in Lublin, ul. Akademicka 15, Lublin, elzbieta.kaczmarska@up.lublin.pl

2 58 E. Kaczmarska lowered vigour of progenies compared with their non-inbred counterparts. Whereas, heterosis or hybrid vigour is defined as the superiority of a F 1 hybrid over its parent [Hedrick and Kalinowski 2000, Stuber 1994]. Inbreeding varies from year to year within the same population and also some life history stages are more susceptible to inbreeding within a population and across taxa [Charlesworth and Charlesworth 1987]. Moreover, a significant correlation exists between inbreeding and selfing/outcrossing species, namely repeated selfing reduces the magnitude of inbreeding [Husband and Schemske 1996, Pico et al. 2007]. Selfing increases homozygosity and more homozygous genotypes may be susceptible to environmental harshness. In contrast, outcrossing usually increases or maintains heterozygosity that tends to produce genotypes better able to buffer themselves against environmental variability [Falconer 1981, Thiemann et al. 2009]. In case of plants, inbreeding is generally estimated based on populations or progenies with known inbreeding levels generated under experimental systems. In most cases randomly mating populations are assumed to have an inbreeding coefficient of zero (F = 0) and are compared with self-pollinated progenies obtained at random from the reference population [Chaves et al. 2010]. Inbreeding in strawberries is difficult to apply because of the strong inbreeding in selfed progenies. Seedlings possess no vigour, are not resistant to diseases and produce very small fruits [Hulewicz and Horty ski 1979]. Lots of seedlings are not winter-hardy enough and die during winter season. Experiments were conducted to estimate the effect of multigenerational inbreeding on different yield contributing characters in the strawberry. MATERIAL AND METHODS The experiments testing the strawberry germplasm were conducted between 2004 and 2010 at the Felin Research Plantation of the University of Life Sciences in Lublin. Ten strawberry cultivars including Kent, Selva, Elkat, Elsanta, Paula, Ostara, Teresa, Senga Sengana, Chandler and the breeding clone 1387 were examined and self-pollinated but only 5 of them developed second and third inbreeding generations. The first self-pollination was performed in May Before flowering time inflorescences were covered with small bags made of cloth and left undisturbed for spontaneous selfing. 150 seedlings (S 1 ) derived from each of the cultivars (non-inbred progenies) were used in field trials on September 10, In May 2006, the second self-pollination was performed. Twenty seedlings randomly chosen from the first-generation self were self-pollinated to generate the secondgeneration self (S 2 ). In 2008 some seedlings were retained from this populations and used as parents to obtain the third-generation self. Progeny S 3 marked with corresponding numbers was derived from the same S 2 parental plants. In the years 2006, 2008 and 2010 the following indices were recorded: number of inflorescences, number of flowers per inflorescences, fruit yield per plant, fruit number per plant, average fruit weight, weight of leaves per plant and vitality of pollen. Data for Acta Sci. Pol.

3 Inbreeding for yield and yield components in Fragaria ananassa Duch. 59 growth and productivity traits were collected for individual plants (non-inbred control and inbreeding populations) throughout the season following the plantation establishment. Weight of leaves per plant was obtained on July 20, after harvest. Yields and fruit numbers were recorded for each plant for 4 consecutive weeks starting from the first week of June. Weight of the single fruit was calculated by dividing weekly yields by corresponding fruit numbers. Pollen viability of 5 strawberry cultivars and their progenies was measured based on the grain colour. One day prior to flowering of each clone, 20 flowers were randomly collected and then microscopic preparations were made. Slides were coloured with 2% solution of acetocarmin and glicerin (1:1) and examined by use of the Olympus BX41 microscope under magnification 400 x. In any combination (the microscopic slide) were analyzed to 100 grains in 10 fields of vision. Pollen grains with % content of cytoplasm were taken as vital. The percentage data of pollen viability were transformed before analysis using the Bliss function Y = arcsine p. Inbreeding (ID) was assesses using means according to the following formula: where: S 0 mean of S 0, S 1 mean of S 1, S 2 mean of S 2, S 3 mean of S 3. S0 S1 ID for S S S0 S2 ID for S S S0 S3 ID for S S Data obtained were statistically evaluated with ANOVA (SAS System software). Results were analysed statistically by means of two-way analysis of variance with use of the Duncan test at the significance level = The Pearson s coefficient () was evaluated for the following traits: number of inflorescences, number of flowers per inflorescences, fruit yield per plant, fruit number per plant and weight of leaves per plant. Data presented in the tables are means for three seasons of the study RESULTS AND DISCUSSION Seeds of 10 cultivars were obtained after the first self-pollination. However, the percentage of germinating seeds was very low 6.8% on average, fluctuating from 0.9% to 18%. The percentage of mature plants obtained from the seedlings was also very low. Three cultivars including: Paula, Selva and Ostara gave no S 1 progeny. Hortorum Cultus 11(1) 2012

4 60 E. Kaczmarska The second self-pollination of Elkat and Elsanta cultivars resulted in the very small number of viable mature plants (9 and 13 individuals), so the number of initial genotypes was strongly reduced. In this research inbreeding (ID) was found to occur in S 1 populations for the studied characters (tab. 1, 2, 3). Among other characters, three characters, namely vitality of pollen (ID = 40.7), yield per plant (ID = 52.5) and weight of leaves per plant (ID = 62.5) were affected the most. In domestic strawberries fruit yield is among the traits the most affected through inbreeding and can be reduced by as much as 80% after two generations of selffertilization [Spangelo et al. 1971, Shaw 1995, 1997 ]. In this experiment ID for fruit weight per plant decreased in successive inbreeding generations and amounted to 52.5 for S 1, 36.6 for S 2 and 22.0 for S 3 (tab. 2, 5, 8). Bellusci at al. [2009] indicates that the magnitude of trait mean depends on the rate at which homozygosity accumulates and the strength of selection pressure counteracting this. Additionally, it is supposed that reciprocal recurrent selection would give more viable and homogeneous inbred lines. The magnitude of mean observed for the first-generation self in this study is consistent with results obtained from urawicz [1990], where strong inbreeding cultivar Dukat caused a very strong reduction in yield compared to the families obtained through sibcrossing and mating non related parents. As fruit yield per plant is concerned, it is worth mentioning that there was a considerable variability of this trait (a wide range observable for each cultivar). Most plants produced very small distorted fruits, the plants themselves were also more compact and smaller than the initial cultivars. The experiments with strawberries have demonstrated significant and occasionally severe trait mean for populations of inbred offspring constructed from matings among current generation relatives; fruit yields decreased significantly even when rather modest rates of inbreeding were applied [Shaw 1995]. During three years of research (2006, 2008, 2010) inbred progenies showed higher variability in relation to the non-inbred control populations in terms of five studied traits, which shows the calculated coefficient of variation (CV %). However, the greatest differences in average fruit yield per plant were observed among individuals (CV about 60%) as shown in table 2, 5 and 8. This is consistent with the results obtained by urawicz [1990], where the calculated CV for Dukat S 1 amounted to 59.4%. A low was found for number of inflorescences and number of flowers per inflorescences (12.7% and 27.8% reduction for the third-generation selfs) (tab.7), and a larger was observed for pollen viability and fruit number per plant (35.0% and 44.5% reduction for the third-generation selfs) (tab. 7, 8). ID for average weight of single fruit appeared at a similar level and equalled 29.6, 27.9 and 29.0 in S 1, S 2 and S 3, respectively. Depression for weight of leaves per plant increased with rising F in S 1, S 2 and S 3, where inbreeding was ID = 62.5, ID = 66.2 and ID = 67.2 (tab. 3, 6, 9), respectively. The trends were similar to those reported earlier for the first-generation [Shaw 1995] and the second-generation inbred ones in the strawberry [Shaw 1997]. Acta Sci. Pol.

5 Table 1. Comparison of yield components of S 0 and S 1 progeny and inbreeding in S 1 generation Tabela 1. Porównanie cech plonotwórczych potomstwa S 0 i S 1 oraz wsobna w pokoleniu S 1 Cultivar /S1 Number of inflorescences Liczba kwiatostanów Odmiana/S1 rednia mean S 1 S0 rednia S1 (ID) Number of flowers per inflorescences Liczba kwiatów w kwiatostanie mean S1 rednia S1 (ID) viable pollen S0 py ek ywotny S0 Pollen viability% ywotno py ku % viable pollen S1 py ek ywotny S1 S. Sengana 8.55ab* a a a cd 17.75c 55.7 Teresa 8.30abc a a a d 19.18c 43.3 Kent 6.23bc a a a bc 19.56c 57.2 Chandler 6.11c a a a ab 43.70a 15.9 Klon a a a a a 38.81a 31.6 Mean rednio 7.63ABC A A A BC 27.80B 40.7 LSD NIRp< (ID) **Coefficient of variation (CV) Wspó czynnik zmienno ci Table 2. Means, coefficient of variation () for cultivars and S 1 progeny and inbreeding in S 1 generation Tabela 2. rednie warto ci cech, wspó czynnik zmienno ci () dla odmian i potomstwa S1 oraz wsobna w pokoleniu S 1 Fruit yield per plant (g) Number of fruit per plant Cultivar /S1 Plon owoców z ro liny (g) Liczba owoców z ro liny Odmiana/S1 mean S1 mean S1 rednia S1 (ID) rednia S1 (ID) Senga Sengana c* bc b a Teresa a ab b a Kent c c b a Chandler d c c a Klon a a a a Mean rednio B BC B A LSD NIRp<

6 Table 3. The means and inbreeding in S 1 progeny in terms of weight of leaves per plant and weight of the single fruit Tabela 3. rednie warto ci cech oraz wsobna w potomstwie S 1 pod wzgl dem masy li ci i masy pojedynczego owocu Weight of leaves per plant (g) Masa li ci z ro liny (g) Weight of fruit (g) Masa pojedynczego owocu (g) Cultivar /S1 Odmiana/S1 mean S1 (ID) mean S1 rednia S1 rednia S1 Senga Sengana ab* ab b 5.16a 17.7 Teresa a abc a 6.45a 36.0 Kent 90.60c c b 4.60a 33.3 Chandler bc bc b 3.61a 41.2 Klon ab a b 5.62a 19.8 Mean rednio AB ABC B 5.09A 29.6 LSD NIRp< (ID) Table 4. Comparison of yield components of S 0 and S 2 progeny and inbreeding in S 2 generation Tabela 4. Porównanie cech plonotwórczych potomstwa S 0 i S 2 oraz wsobna w pokoleniu S 2 Cultivar /S2 Number of inflorescences Liczba kwiatostanów Odmiana/S2 rednia mean S 2 S0 rednia S2 (ID) Number of flowers per inflorescences Liczba kwiatów w kwiatostanie mean S2 rednia S2 (ID) viable pollen S0 py ek ywotny S0 Pollen viability % ywotno py ku % viable pollen S2 py ek ywotny S2 S. Sengana 11.30a* ab ab b ab 20.71b 60.4 Teresa 14.75a a a a ab 29.75ab 42.3 Kent 12.35a ab b b b 32.30ab 20.3 Chandler 13.62a a ab ab a 45.82a 18.2 Klon a b ab ab a 44.67a 26.5 Mean rednio 12.61A AB AB AB AB 34.65AB 33.5 LSD NIRp< (ID)

7 Table 5. Means, coefficient of variation () for cultivars and S 2 progeny and inbreeding in S 2 generation Tabela 5. rednie warto ci cech, wspó czynnik zmienno ci () dla odmian i potomstwa S 2 oraz wsobna w pokoleniu S 2 Cultivar /S2 Odmiana/S2 Fruit yield per plant (g) Plon owoców z ro liny (g) mean S2 rednia S2 (ID) Number of fruit per plant Liczba owoców z ro liny mean S2 rednia S2 (ID) S. Sengana b* bc ab a Teresa a a a ab Kent c c b c Chandler c bc b b Klon b b ab b Mean rednio B B AB B LSD NIRp< Table 6. The means and inbreeding in S 2 progeny in terms of weight of leaves per plant and weight of the single fruit Tabela 6. rednie warto ci cech oraz wsobna w potomstwie S2 pod wzgl dem masy li ci i masy pojedynczego owocu Weight of leaves per plant (g) Masa li ci z ro liny (g) Weight of fruit (g) Masa pojedynczego owocu (g) Cultivar /S2 Odmiana/S2 mean S2 (ID) mean S2 rednia S2 rednia S2 S. Sengana b* a a 3.58a 33.9 Teresa a ab a 5.08a 22.8 Kent 98.07b ab a 4.16a 19.4 Chandler b b a 4.04a 29.9 Klon b b a 4.18a 33.6 Mean rednio B AB ,2 5.84A 4.21A 27.9 LSD NIRp< (ID)

8 Table 7. Comparison of yield components of S 0 and S 3 progeny and inbreeding in S 3 generation Tabela 7. Porównanie cech plonotwórczych potomstwa S 0 i S 3 oraz wsobna w pokoleniu S 3 Cultivar /S3 Odmiana/S3 Number of inflorescences Liczba kwiatostanów rednia mean S 3 S0 rednia S3 (ID) Number of flowers per inflorescences Liczba kwiatów w kwiatostanie mean S3 rednia S3 (ID) viable pollen S0 py ek ywotny S0 Pollen viability % ywotno py ku % viable pollen S3 py ek ywotny S3 derpession (ID) S. Sengana/(17) 10.70ab* bc b b ab 35.91a 30.1 Teresa/(18) Teresa/(21) Teresa/(25) 7.93bc 8.86ab d 9.30abc ab 9.33a a 6.51a ab 32.30ab 40.5 Kent/(7) 6.66b cd b ab b 36.25a 2.8 Chandler/(122) Chandler/(123) 9.55ab 11.61a bc b 5.11a a ab 22.64c 55.1 Klon 1387/(35) 14.00a ab b ab a 29.04b 46.3 Mean rednio 9.95AB BC B A AB 31.23B 35.0 LSD NIRp<

9 Table 8. Means, coefficient of variation () for cultivars and S 3 progeny and inbreeding in S 3 generation Tabela 8. rednie warto ci cech, wspó czynnik zmienno ci () dla odmian i potomstwa S 3 oraz wsobna w pokoleniu S 3 Fruit yield per plant (g) Plon owoców z ro liny (g) a a 38.1 Number of fruit per plant Liczba owoców z ro liny Cultivar /S3 mean S3 mean S3 Odmiana/S3 rednia S3 (ID) rednia S3 (ID) S. Sengana/(17) bc* f b de Teresa/(18) 90.40e cde Teresa/(21) 68.32f e Teresa/(25) a b Kent/(7) b cd ab bc Chandler/(122) ab c a Chandler/(123) bc c b Klon 1387/(35) b cd ab bcd Mean rednio BC D B BC LSD NIRp< ** Coefficient of variation (CV) Wspó czynnik zmienno ci Table 9. The means and inbreeding in S3 progeny in terms of weight of leaves per plant and weight of the single fruit Tabela 9. rednie warto ci cech oraz wsobna w potomstwie S 3 pod wzgl dem masy li ci i masy pojedynczego owocu Weight of leaves per plant (g) Masa li ci z ro liny (g) a 34.4 Weight of fruit (g) Masa pojedynczego owocu (g) Cultivar /S3 mean S3 (ID) mean S3 (ID) Odmiana/S3 rednia S3 rednia S3 S.Sengana/(17) bc bc bc 5.07ab 17.8 Teresa/(18) 47.73a ab 39.6 Teresa/(21) 30.35cd a 6,29a 30.3 Teresa/(25) 47.06a ab 34.6 Kent/(7) 75.00c b a 4.71ab 41.6 Chandler/(122) 27.90d b bc c Chandler/(123) 44.13a ab Klon 1387/(35) ab bc a 4.87ab 45.2 Mean rednio BC B AB 5.17AB 29.0 LSD NIRp<

10 66 E. Kaczmarska Among the studied genotypes, inbred progenies of Chandler were distinguished through another reaction to the selfing there was an increase in number of inflorescences per plant (in S 1, S 3 ), number of flowers per inflorescences (in S 1, S 3 ), yield of fruits (in S 3 ), number of fruits per plant (in S 1, S 2 and S 3 ). Hulewicz and Horty ski [1972] claim that fruit development in strawberries is strictly dependent on the number of fertilized ovules, which stimulate the receptacle to develop around the growing seed by way of secreting substances. The degree of selfcompatibility in different cultivars of the strawberry is largely variable and so is their pollen fertility. Good pollen viability is of great importance in culturing strawberries under glasshouse conditions, in which number of pollinating insects is very limited. In current evaluations average pollen vitality values in parental plants ranging from 45.7% to 52.3% and inbreeding for this trait ranged from 33.5 in S 2, to 40.7 in S 1 as shown in table 1, 4 and 7. Fragaria ananassa (2n = 2x = 56) is a complex polyploidy with multiple independent genomes, because it is a hybrid produced from a cross between the two New World octoploid strawberry species, F. chiloensis and F. virginiana. From alloautopolyploidy nature may be due high sensitivity of this species for inbreeding. Different cross combinations were tested for developing high yielding hybrid strawberry cultivars and some of them were found to be promising. The strawberry, traditionally, is vegetatively multiplied species and therefore, the obtained F 1 hybrids may become the initial forms for new cultivars. To sum up, it is concluded that the response of the strawberry to repeated inbreeding does not differ from that of other plant species because the mechanisms (i. e. the partial dominance and/or overdominance hypotheses) that contribute to inbreeding are universal. CONCLUSIONS 1. After the first and the second self-pollination, plant viability decreased considerably, which made developing progeny practically impossible in case of many genotypes. 2. Some of the tested cultivars, namely: Paula, Selva and Ostara produced no viable S 1 plants. Others such as Elkat and Elsanta gave no S 2 progeny. 3. Average fruit yield per plant in inbred lines of strawberry appeared to be much lower than that of the standard cultivars (inbreeding for this trait decreased in successive inbreeding generations and amounted to 52.5 for S 1, 36.6 for S 2 and 22.0 for S 3 ). 4. As a result of strong inbreeding, weight of leaves per plant in S 1, S 2 and S 3 was affected the most (inbreeding ID = 62.5, ID = 66.2 and ID = 67.2, respectively). 5. The greatest variability among the tested traits in the inbred generations was observed in terms of fruit yield per plant. 6. The percentage of viable pollen in subsequent inbred generations (S 1, S 2 and S 3 ) was lower as compared with the parental forms. Acta Sci. Pol.

11 Inbreeding for yield and yield components in Fragaria ananassa Duch. 67 REFERENCES Alam M.F., Khan M.R., Nuruzzaman M., Parvez S., Swaraz A..M., Genetic basis of heterosis and inbreeding in rice (Oryza sativa L.). J Zhejiang Univ. SCI, 5(4), Bellusci F., Pellegrino G., Musacchio A., Different levels of inbreeding between outcrossing and selfing Serapias species. Biologia Plantarum, 53(1), Charlesworth D., Charlesworth B., Inbreeding and its evolutionary consequences. Ann. Rev. Ecol. Evol., 18, Chaves L.J., Vencovsky R., Silva R.S.M., Zucchi M.I., Estimating inbreeding in natural plant populations using quantitative and molecular data. Conserv. Genet., 10, 1007, Falconer D.S., Introduction to Quantitative Genetics. Second Ed. Longman Press, London. Hedrick P.W., Kalinowski S.T., Inbreeding in conservation biology. Ann. Rev. Ecol. Evol., 31, Hulewicz T., Horty ski J., Self-compatibility and fruit development in some cultivars of strawberry (Fragaria ananassa Duch.). Genetica Polonica, 13 (1), Hulewicz T., Horty ski J., Effect of inbreeding and its use in strawberry breeding. Genetica Polonica, 20(4), Husband B.C., Schemske D.W., Magnitude and timing of inbreeding in a diploid population of Epilobium angustifolium (Onagraceae). Heredity. 75, Pico F.X., Mix C., Ouborg N.J., Van Groenendael J.M., Multigenerational inbreeding in Succisa pratensis: effects on fitness components. Biol. Plant., 51, Shaw D.V., Comparison of ancestral and current-generation inbreeding in an experimental strawberry breeding population. Theor. Appl. Genet., 90, Shaw D.V., Trait mean for second-generation inbred strawberry populations with and without parent selection. Theor. Appl. Genet., 95, Spangelo L.P.S., Hsu C.S., Fejer S.O., Watkins R., Inbred line x tester analisis and the potential of inbreeding in strawberry breeding. Can. J. Genet. Cytol., 13, Stuber C.W., Heterosis in plant breeding. Plant Breed. Rev. 12, Thiemann A., Meyer S., Scholten S., Heterosis in plants: Manifestation in early seed development and prediction approaches to assist hybrid breeding. Chinese Sci. Bull., 54(14), urawicz E., Odziedziczalno najwa niejszych cech u ytkowych truskawki (Fragaria ananassa Duch.). Wyd. ISK Skierniewice. DEPRESJA WSOBNA POD WZGL DEM PLONU I CECH PLONOTWÓRCZYCH U Fragaria ananassa Duch. Streszczenie. U ro lin depresj inbredow szacuje si, porównuj c ywotno pojedynków uzyskanych poprzez samozapylenie z pojedynkami krzy uj cymi si swobodnie. W pracy badano wp yw chowu wsobnego na plon owoców i cechy plonotwórcze u truskawki (Fragaria ananassa Duch.). Do wiadczenia zosta y przeprowadzone w latach w Gospodarstwie Do wiadczalnym UP w Felinie. Badano 10 odmian truskawki: Kent, Selva, Elkat, Elsanta, Paula, Ostara, Teresa, Senga Sengana, Chandler i klon hodowlany 1387, które samozapylano w celu uzyskania kolejnych potomstw wsobnych: S 1, S 2 i S 3. Po dwóch kolejnych cyklach samozapylenia znaczna cz Hortorum Cultus 11(1) 2012

12 68 E. Kaczmarska siewek S 1 i S 2, wywodz cych si od 5 odmian, zamar a na skutek silnego spadku wigoru. Pi pozosta ych odmian zró nicowanych pod wzgl dem pochodzenia, o wspó czynniku wsobno ci (F) przyj tym jako zero (F = 0), porównywano z trzema pokoleniami wsobnymi o spodziewanym wspó czynniku wsobno ci F = 0,5 (S 1 ), F = 0,75 (S 2 ) i F = 0,87 (S 3 ). Efekty ró nego poziomu wsobno ci oszacowano dla nast puj cych cech: liczby kwiatostanów, liczby kwiatów w kwiatostanie, plonu owoców z ro liny, liczby owoców z ro liny, redniej masy owocu, masy li ci z ro liny i ywotno ci py ku. U potomstwa stwierdzono zarówno dodatni, jak i ujemn depresj wsobn pod wzgl dem badanych cech. Depresja inbredowa w pokoleniach S 1, S 2 oraz S 3 najsilniej przejawi a si pod wzgl dem masy li ci z ro liny (wynosi a ona odpowiednio: ID = 62,5; ID = 66,2 i ID = 67,2). W pokoleniu S 2 rednia liczba owoców z ro liny zwi kszy a si w stosunku do S 0 o 6,1%. W kolejnych pokoleniach wsobnych zmniejszy si poziom depresji pod wzgl dem redniej masy owoców z ro liny i wynosi odpowiednio: 52,5 w S 1 ; 36,6 w S 2 oraz 22,0 w S 3. S owa kluczowe: ID, truskawka, plon owoców, chów wsobny Accepted for print Zaakceptowano do druku: Acta Sci. Pol.